Force
Momentum
adverb, noun
This is a single kanji with an い on the end, which means you might think this is an adjective, but it's actually a noun! What's the noun form of force? It's also something's force or momentum.
Since this word consists of a kanji with hiragana attached, it uses the kun'yomi reading. You haven't learned that reading yet, so here's a mnemonic to help you:
The monster that has more force than any other is the icky oil (いきおい) monster. It's the spirit of the hot, icky oil from the deep friers at fast food chains, and nothing will stop that giant mass of icky oil from hurtling at its target.
あの高校生のビデオへの批判の勢い、また強くなったね。
The momentum of criticism over that high school student's video has picked up again, huh?
みんなが食べるというので、勢いで私もイナゴのツクダニを食べた。
Everyone said they were gonna eat it, so in the heat of the moment I ate the locust tsukudani, too.
私達の犬は、誰と競争している訳でもないのに、いつもすごい勢いでミルクボーンに向かって行きます。
Our dog always bolts towards the milk-bone even though he isn’t racing anyone.